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Bioassay-guided fractionation of the cytotoxic leaf extract of Vernonia pachyclada Baker led to the isolation of three new sesquiterpene lactones, designated glaucolides K−M (1−3). The structures of the new compounds were determined using 1D and 2D NMR spectroscopy, and the structure and stereochemistry of 1 were confirmed by single-crystal X-ray diffraction. Compound 3 showed moderate activity in the A2780 human ovarian cancer cell line, with an IC50 of 3.3 μM.

The new glycoresins, ipomoeassins A−E (1−5), have been isolated from the leaves of Ipomoea squamosa. The structures were elucidated by spectroscopic analyses and chemical transformations. The absolute configurations of C-5 (ipomoeassins 3−5) and C-11 (ipomoeassins 1 and 2) were determined by their derivatives with (R)- and (S)-MPA. All the isolates were active in the A2780 human ovarian cancer cell line assay, and 4 showed the highest activity with an IC50 value of 35 nM.

Bioassay-guided fractionation of an EtOAc extract of the leaves of Melampodium camphoratum using an assay for inhibitors of the degradation of hemin resulted in the isolation of six new eudesmane sesquiterpenes (1−6) and the known 6-epi-β-verbesinol coumarate (7). The structures of compounds 1−6 were established as 6α-(4‘-O-methyl-7‘E-coumaryloxy)eudesm-4(14)-ene (1), 6α-({4‘-O-stearyl}-7‘E-coumaryloxy)eudesm-4(14)-ene (2), 6α-({4‘-O-palmityl}-7‘E-coumaryloxy)eudesm-4(14)-ene (3), 6α-({4‘-O-[9‘ ‘Z-hexadecenoyl]}-7‘E-coumaryloxy)eudesm-4(14)-ene (4), 6α-(7‘Z-coumaryloxy)eudesm-4(14)-ene (5), and 6α-({4‘-acetoxy}-7‘Z-coumaryloxy)eudesm-4(14)-ene (6). Compounds 1−4 showed weak activity in the hemin degradation assay, while compounds 5−7 were inactive.

Bioassay-guided fractionation of the cytotoxic MeOH extract obtained from Acridocarpus vivy led to the isolation of five new triterpenoids, acridocarpusic acids A−E (1−5); three known triterpenoids, moronic acid (6), ursolic acid, and oleanolic acid; and two known flavonoids, 4‘,5-dihydroxy-7-methoxyflavone and 4‘,5-dihydroxy-3‘,7-dimethoxyflavone. The structures of the new compounds 1−5 were established on the basis of extensive 1D and 2D NMR spectroscopic data interpretation. Compound 3 showed significant cytotoxic activity in the A2780 assay, with an IC50 value of 0.7 μg/mL.

Bioassay-directed fractionation of a methyl ethyl ketone extract of the roots of Endlicheria aff. resulted in the isolation of four new neolignans (1−4) and eight known compounds, namely, canellin A (5), canellin C (6), 3‘-methoxyguianin (7), (7S,8R,1‘S,5‘S,6‘R)-Δ^2‘,8‘-3‘,6‘-dihydroxy-5‘-methoxy-3,4-methylenedioxy-4‘-oxo-8.1‘,7.5‘-neolignan (8), armenin-B (9), dillapiole (10), 1-allyl-2,6-dimethoxy-3,4-methylenedioxybenzene (11), and ω-hydroxyisodillapiole (12). The structures of the new compounds (1−4) were established as (7S,8R,1‘S,5‘S,6‘R)-Δ^2‘,8‘-5‘,6‘-dihydroxy-3‘-methoxy-3,4-methylenedioxy-4‘-oxo-8.1‘,7.5‘-neolignan, (7S,8R,1‘S,5‘S,6‘R)-Δ^2‘,8‘-3‘,5‘,6‘-trihydroxy-3,4-methylenedioxy-4‘-oxo-8.1‘,7.5‘-neolignan, 2,4-dimethoxy-5,6-methylenedioxy-1-(2-propenyl)benzene, and 2,6-dimethoxy-3,4-methylenedioxycinnamyl alcohol, respectively, on the basis of spectroscopic interpretation.

Continuation of the chemical examination of the cytotoxic constituents of the wood of Vepris punctata resulted in the isolation of the two new terpenoids 1 and 2 and eight known compounds, glechomanolide (3), isogermafurenolide, (E,E)-germacra-1(10),4,7(11)-triene, α-amyrin, lupeol, lupeyl acetate, taraxerol, and 3-epi-taraxerol, in addition to the alkaloids reported reported previously. The structures of the two new compounds were established on the basis of 1D and 2D NMR spectroscopic data interpretation and chemical modifications. All the isolated compounds were tested against the A2780 human ovarian cancer cell line; the four sequiterpenoids showed moderate cytotoxic activity, while the six triterpenoids were inactive.

The female steroid hormone 3,17β-estradiol (2) was selected as an agent to target taxol (1) to estrogen receptor (ER) positive breast cancer cells. Estradiol−taxol conjugates (ETC) were synthesized through linkages from the 11- or 16-position of estradiol to the 2‘-, 7-, or 10-position of taxol. All conjugates were cytotoxic to the A2870 ovarian cancer cell line, although less so than taxol. The MCF-7 breast cancer cell line (ER-α positive) and MDA-MB-231 breast cancer cell line (ER-α negative) were also used to evaluate the selectivity and cytotoxicity of these conjugates. One conjugate showed some selectivity for ER positive cells, but it was less potent than taxol. Two ETC hemisuccinates were also prepared to improve the solubility of the conjugates. The corresponding Na and triethanolammonium salts were slightly more cytotoxic than the acid form but were much less cytotoxic than the corresponding ETC.